Catalysts for the polymerization of butadiene-1, 3 hydrocarbons



- Patented Feb. 25, 1947 2,416,461 FlCE I CATALYSTS FOR. THEPOLYMERIZATION F BUrAnmNn-Ls HYDRQCABBONS I William D. Stewart, Akron,Ohio, assignor to The B. F.: Goodrich Company, New York, N Y., acorporation oi New York No Drawing. Application February. 13, 1943,Serial No. 475,796. In Canada'February 19,

Claims., (01. zoo-ass) This invention relates to the polymerization inaqueous emulsion of butadiene-1,3 hydrocarbons either alone or inadmixture with each other or with other unsaturated organic compounds.copofymerizable therewith in aqueous emulsion, and bases its principalobject to provide new catalysts or accelerators for such polymerizationsby the use of which improved polymers may be obtained in increased yieldand in a very short interval of time. This application is acontinuation-in-part of my copending application Serial No. 879,712filed February 19, 1941. i

Ithas already been praposed in U. S. Patent 1,935,733 to Tschunkur andBook to polymerize butadiene-1,3 hydrocarbons in presence of anoxidizing agent and a metallic salt such as the salts of cobalt, lead,manganese, chromium and nickel. In the process of that patent, however,the metallic salt, which may be either a soluble or insoluble salt, isadded in concentrations greater than 1 part of the salt, to 200 parts ofthe butadiene, or greater than 0.5% based on the material polymerized,and polymerization is effectedonly after allowing an emulsion containingthe butadiene, oxidizing agent and metallic salt to stand for a few daysat a temperature of 60 C.

I have now discovered that the presence of exceedingly small amounts, ofsimple watersoluble salts of certain metallic elements, either with orwithout the simultaneous presence of known initiators and acceleratorsoi polymerization such as oxidizing agents, greatly increases bromides,sulfates, sulfites, nitrites, thiocyanates,

they are water soluble.

the speed 01' polymerization of butadiene-1,3 hydrocarbons and enablessuch polymerizations to be effected in only a few hours and at atemperature of only 20-30 C. Since lower temperatures for polymerizationmay be employed, products of improved physical properties may beobtained Accordingly, this invention is concerned with the use of smallconcentrations of simple watersoluble salts of metallic elements ascatalysts for .the aqueous emulsion polymerization of buta- I group II-Bmetals.

The term water-soluble" as applied to these metal salts is used tosignify that the salts are appreciably soluble in water, at least to theextent of 0.1 g. in 100 cc. of water at 20 C., while the etc., of any 01the metals named above provided Water-soluble salts to! these metalswith organic acids such as the ace tates, formates, oxalates, tartratesand citrates may also be employed. Either the oxidized or reduced formof those metals capable of existing in more than one valence iseffective, for example,

both mercurous chloride and mercuric chloride are operable. Mixed salts,acid salts and basic salts which are water soluble as well as watersoluble salts wherein the metal is a part of the anion, sodium zincatefor example, may also be used.

' The concentration of these salts in the emulsion to be polymerized isa critical part of the invention since the remarkable catalytic effectof these salts on polymerization is exerted only when -.smallconcentrations are used.' In general the amount of salt should notexceed 0.1% of the quantity of material polymerized nor should it exceed0.1% of the quantity of water present in the emulsion. Since a, largeramount of water than of monomers is normally present when conductingpolymerization in aqueous emulsion, the concentration of salt based onthe material polymerized is the limiting factor. Preferably, from about0.001 to 5 parts of the metallic-salt for each 10,000 parts of materialpolymerized, that is, fro 0.00001 to 0.05%, should be employed.

As has been mentioned hereinabove, the metal salt catalysts of thisinvention may be used in the polymerization in aqueous emulsion of anyoi the butadiene- 1,3 hydrocarbons by which is meant butadiene-1,3itself and'its hydrocarbon homologs which polymerize in essentially thesame manner such as isbprene, 2,3-dimethyl butadime-1,3, piperylene,etc., either alone or in admixture with each other and/or in admixturein aqueous emulsion.

with ,butadiene-1,3 hydrocarbons in aqueous with one or more otherunsaturated organic compounds which are copolymerizable therewithMonomers copolymerizable disconnected valences is attached to a groupmore electronegative than alkyl groups. ypical ...g... ll

structure such as carboxy and ester groups, cyano groups, halogen, etc.Vinyl and vinylidene compounds particularly are generallycopolymerizable withbutadiene-LB hydrocarbons in aqueous emulsion.Specific monomers copolymerizable with butadiene-1,3 hydrocarbons inaqueous emulsion include styrene, p-chloro styrene, pmethoxy styrene,vinyl naphthalene, acrylonitrile, methacrylonitrile, acrylic acid,methacrylic acid, methyl acrylate, butyl acryiate, methyl methacrylate,ethyl methacrylate, methacrylamide, methyl vinyl ketone, methylisopropenyl ketone, vinylidene chloride, vinyl furane, diethyl fumarate,chloroprene and the like. It is preferable in this invention, that thesecopolymerizable monomers, when polymerized in admixturewith butadiene-1,3 hydrocarbons, be present in minor proportions by weight sincemonomer mixtures containing predominant amounts of butadiene-1,3hydrocarbons yield synthetic rubbers when polymerized. However, thecatalysts of this invention may be employed when any mixture of abutadiene-1,3 hydrocarbon with a monomer copolymerizable therewith iscopolymerized in aqueous emulsion.

In the practice of the invention the monomer or monomer mixture to bepolymerized is emulsified in water with-the aid of an emulsifying agentto form an aqueous emulsion. Preferably the water-soluble metal salts ofthis invention are then added to the emulsion together, if desired, withvarious other substances, such as polymerization initiators,polymerization accelerators, polyvmerization modifiers, or even otherpolymerizapolymerized and the metal salt catalysts in the properconcentration is then preferably agitated at a temperature of about20-l00 C, until polymerization is substantially complete. This usuallyrequires from 5 to 50 hours at 30 C. or an even shorter time at highertemperatures. The resulting polymerized product is in the form of alatexlike dispersion which may be coagulated in the usual way to yieldthe solid polymer.

Emulsifying agents which-may be used in the above process includepartially or completely neutralized fatty acid soaps such as sodiumoleate and sodium myristate,. hymolal sulfates and sulfonates such assodium lauryl sulfate and sodium isobutyl naphthalene sulfonate, andother well-known emulsifying agents. f

Polymerization initiators which are preferably but not essentiallypresent in the emulsion during the'polymerization includeoxygen-yielding com pounds such as hydrogen peroxide, organic peroxides,potassium persulfate, sodium perborate, sodium periodate, potassiumpercarbonate, oxygen, ozonides and the like. The catalysts of thisinvention may also be employed when the polymerization is initiated byother types of initiators such as diazoamino benzene and sulfur dioxide.

Polymerization modifiers such as dialkyl di-v xanthogens, mercaptans,tetra-alkyl thiuram disulfides and other sulfur-containing organic com--pounds which enable polymers of increased solubility and plasticity tobe prepared may also be present in the emulsion during thepolymerization.

It is believed that the function of the metal salts employed incatalyzing polymerization re-H oxidation-reduction reactions; and thatthe oxidation reduction reactions occurring activate the monomermolecules to such an extent that they are then capable of adding on toone another in.

a rapid chain reaction which finally produces the polymer. This samefunction is also believed to be exerted by many other catalystscontaining a heavy metal combined with various other compounds such aspyrophosphates, laevulinic acid, glycine, beta-mercapto ethanol,quebrachitol, cholesterol and the like, which catalysts are more fullydisclosed in my copending applications Serial Nos. 379,713 to 379,717filed February 19, 1941.

As an example of the method of carrying out the invention and in orderto illustrate the desirable results obtained by employing thewatersoluble salts of metals occurring in groups 11 to VI of theperiodic table as catalysts for the emulsion polymerization ofbutadiene-1,3 hydrocarbons, an aqueous emulsion containing the followingingredients. is prepared:

This emulsion is then agitated at 30 C. for 29 hours whereuponpolymerization is complete and a latex-like dispersion is obtained. Uponcoagulating the latex a 98% yield of a strong plastic rubberybutadiene-1,3 acrylonitrile copolymer is obtained. When a similaremulsion not containing the zinc sulfate is polymerized-under the sameconditions,'i"45 hours are required to produce a 98% yield.

In other embodiments of the invention aqueous emulsions containingbutadiene-1,3 and acrylonitrile prepared as indicated above arepolymerized at 30 C. in the presence of various salts of metalsoccurring in groups II to VI of the periodic table. The increase inspeed of polymerization brought about by the presence of these salts isshown'as follows:

- Confienlration o l; P t 1 1d sn per con er cen y e Metal sun by weightbased after 14 hrs.

on monomers) None (control) 56 Mercuric chloride 0. 01 Magnesiumsulfate... 0. 01 67 Calcium chloride..." 0. 01 65 Strontium chloride.0.01 (15 Aluminum sulfa 0.01 67 Cork: sulfate 0.01 76 It is seen that inall cases thepresence of the -metal salt. increased the polymerizationrate.

Whereas the emulsions containing the metal salt were completelypolymerized in 38 hours or less time, the emulsion not containing themetal salt required 45 hours for completion.

is polymerized at 30 C.

. In still another embodiment oi .the invention an emulsion containingthe following ingredients Parts Butadiene-1,3 70 Styrene 30 Water 250Fatty acid soap 5 l Hydrogen peroxide 1 0.35 Polymerization modifier0.45 Mercuric chloride 0.02

The polymerization requires 43 hours to produce a 96% yield of a plasticsynthetic rubber. In the absence of the mercuric chloride the poly--merization requires over 150 hours.

It will be obvious to those skilled in the art that many modificationsin the nature and proportions oi. materials polymerized, in thenature ofthe metallic salt and in the nature and proportion of the othersubstances present in the emulsion may be made in the above specificexamples, in accordance with the broad disclosure herein, withoutdeparting from the spirit and scope of the invention as defined by theappended claims.

I claim: 4,

1. The method which comprises preparing an aqueous emulsion containingwater and a'lesser amount. of polymerizable material comprising abutadiene-I'B hydrocarbon, adding to the water of said emulsion fromabout 0.00001 to 0.05% by weight based on the total polymerizablematerial present of a simple ioniz'able salt of a metal occurring ingroup 11-13 or the periodictable, the

- said salt being one which is capable oi dissolving in water at leastto the extent of 0.1 g. in 100 cc. of water at 20 C., and polymerizingthe butadir ene-1,3 hydrocarbon in the aqueous emulsion in the presenceof the added salt, whereby the rate of polymerization is' substantiallyincreased.

2. The method of claim 1 wherein the metal merizable therewith inaqueous emulsion, adding to the water of said emulsion from about0.00001 to 0.05% by weight based on the monomeric mixture of a simpleionizable salt of a metal Occurring in Group 11-3 01' the periodictable,.the said salt being one which is capable of dissolving in waterat least to the extent oi 0.1 g. in 100 cc. of

water at 20 0., and polymerizing the said monomeric mixture in theaqueous emulsion in the presence-oi the added salt, whereby the rate ofpolymerization is substantially increased.

5. The method of claim 4 further characterized in that thepolymerization or the monomeric mix- 6 r ture in aqueous emulsion iseflected in the presence of an oxygen-yielding initiator of po yerization.

6. The method of claim 4 wherein the monomeric mixture is a mixture ofbutadiene.-1,3 and acrylonitri le.

7. The method which comprises preparing an aqueous emulsion containingwater and a lesser amount of a monomeric mixture of butadiene-1,3 andanother unsaturated compound copolymerizable therewith in aqueousemulsion, adding to the water of said emulsion about 0.01% by weight:based on the monomeric mixture of a simple ionizable salt of a metaloccurring in group 11-3 of the periodic table, the said salt being onewhich is capable of dissolving in water at least to the extent of 0.1 g.in 100 cc. of water at 20 C., and polymerizing the said monomericmixture in the aqueous emulsion in thepresence of the added salt,whereby the rate of polymerization is substantially increased.

8. The method or claim '7 wherein the monomeric mixture is -a mixture ofbutadiene-1,3 and acrylonitrile.

9, The method which comprises preparing anaqueous emulsion in thepresence of the mercuric chloride, whereby the rate of polymerization issubstantially increased.

v 10. The method of claim 9 further characterized in that thepolymerization of the monomeric mixture in aqueous'emulsion is efl'ectedin the presence 01. hydrogen peroxide.

' WILLIAM D. STEWART.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED'STATES PATENTS OTHER REFERENCES Pages744-747, "Langes Handbook ofChemistry, pub. 1944, by Handbook Publishers Inc San- ,dusky, Ohio. 1 cL

